1) Field of the Invention
The present invention relates to a microscope having an optical element that is provided with an anti-reflection film applied to a surface thereof used in ultraviolet, visible, and infrared regions.
2) Description of Related Art
In general, surfaces of optical components such as lens and prism are processed with anti-reflection films. The main purpose of this treatment is to improve transmittance of an entire optical apparatus constructed of a number of optical components, specifically, to improve brightness and conspicuousness of images by staying reflection of visible-region light. Since many of the conventional optical apparatuses have been used in the visible region or wavelengths region narrower than that, it has been only necessary for anti-reflection films also to reduce reflectance in such a narrow wavelength region.
In recent years, however, upon emergence of optical apparatuses designed for use in wider wavelength regions, anti-reflection films for the corresponding wavelength regions are required for optical components used in such apparatuses. An example of the conventional anti-reflection film for a wider wavelength region is disclosed in Japanese Patent Publication No. 2711697. In this Publication, by configuring an eight-layer structure using three materials, or TiO2, SiO2, and MgF2, a low reflectance as not being greater than 0.8% is achieved over a wide range from the visible region to the infrared region.
Besides, for recent optical apparatuses, there are required anti-reflection films or optical components that achieve high anti-reflection performance and high transmittance in the near-ultraviolet region (350 nm˜400 nm) also, in addition to the visible region (400 nm˜700 nm) and the infrared region (600 nm˜900 nm). In microscopy, for example, for the purpose of simultaneously proceeding the observation technique that uses light in the ultraviolet region or the infrared region as a probe, to be specific, for the purpose of observing light in the visible region and light in the infrared region emitted from a sample in response to excitation by irradiation with light in the ultraviolet region, in addition to the purpose of improving conspicuousness in the visible region for viewing by eyes, high transmittance and anti-reflection performance over the ultraviolet region through the infrared region has been much required.